SPACE EXPLORATION INITIATIVE
AUTOMATION & ROBOTICS
TRADE STUDY

AUTOMATION ANALYSIS REPORT

One of the most promising results of establishing a permanent manned
outpost on the moon is the capability of producing sufficient oxygen
to be used as a fuel to power spacecraft to Mars [33]. The capability of
producing oxygen on the moon is also essential to achieving the
ultimate goal of establishing a self-sufficient base on the moon by
providing oxygen for breathing and for fueling reusable landers.
Approximately 40% by weight of lunar surface material is oxygen,
in the form of metal oxides of aluminum, iron, titanium, and
silicon.
This subreport includes this introduction (1.0), Task Overview
(2.0), Issues Concerning Automation of the LLOX Production
Facility (3.0), Conclusions (4.0), and References (5.0).

2.0 Task Overview

The lunar surface is a rich source of many minerals, from which
many elements can be isolated. Appendix E considers the general
issues of lunar soil exploitation. "The ability to delineate,
mine, and process materials found on the lunar surface is an
essential factor in the establishment of man's long-term presence
in space.... The act of mining, or removing material (ore) from
its natural environment, is a process which may be accomplished
in many different ways" [24].
Criswell et. al. [5] suggested that one could reasonably attempt
to recover by chemical means any of the 7 "major elements" in
lunar material (oxygen, aluminum, calcium, iron, magnesium,
silicon, and titanium), and that 6 "minor elements" (chromium,
manganese, sodium, potassium, sulfur, and phosphorus) could be
recovered in the course of major element processing, but that it
would not be practical to recover the minor elements by chemical
means solely for their own content.
Of the trace elements, they only considered recovery by
vacuum pyrolysis of the four light solar wind elements
(hydrogen, helium, carbon, and nitrogen).
More detailed considerations of the possibility of magnetic
extraction of lunar free metals combined with a proposed
electrorefining process for an iron-nickel-cobalt alloy suggests
that all three metals are potentially recoverable.
This report concentrates on the extraction, storage, and processing
of oxygen, with a view to assessing the required degree of
automation.
Electrochemical experiments [10] have demonstrated the
feasibility of extracting iron and oxygen from simulated lunar
magma (molten rock). This is probably a required step in several
of the reducing liquid-liquid extraction methods of chemical
beneficiation (see Appendix E) to achieve reasonable enrichments
of other trace elements without excessive dilution by molten
iron. For this purpose it may be essential that the iron be
removed in the solid rather than the molten state, which may
impose constraints on the level of eutectic forming elements such
as silicon or aluminum in the cathode and the melting temperature
of the residual magma, especially as the iron content is deleted.
Of course, material at or near the temperature of molten iron is
hazardous for human beings, and therefore automation requirements
are imposed by the very nature of high-temperature processing.
Currently twenty-seven processes are receiving major
consideration for use in the extraction of oxygen from lunar regolith.
Some of the leading candidates are ilmenite reduction [29],
magma partial oxidation [23], and magma electrolysis [28].
Since a decision has not been made between these processes,
this section will avoid, as much as possible,
paying special attention to any of these processes [30].
Some examples of differences between these processes, by way of
illustration, are:
(1) Ilmenite reduction imposes a heavy requirement on crushing
and grinding (see Appendix E discussion of preconditioning and
beneficiation).
(2) Magma electrolysis can utilize regolith scooped up from
immediately around the process plant, and so there is a reduced
requirement for ore processing or transport (see 2.7 for an
alternative to regolith haulers).
(3) In general, materials handling, preconditioning, and
beneficiation requirements are functions of the process chosen
for oxygen production.
The large scale production of oxygen on the moon will require well
organized activities of several components. Ore will be mined and
loaded into a regolith hauler (but see 2.7 for an alternative).
The hauler will transport the ore to a pre-processing facility
which will crush and screen the ore then load it onto a feeder belt
or hopper. This feeder will load the ore into the processing facility
which will extract the oxygen and any other components of value
from the ore. The tailings will be removed from the processing facility
and transported to a dump site. The oxygen will be liquified and
stored in tanks. The majority of these tasks are covered in other
sections of this document and will not be covered here.
Why do we consider only the large-scale production of oxygen?
One reason is that the adoption of chemical beneficiation steps
(other than vacuum pyrolysis) is predicated [5] on the
establishment of a substantial mass handling facility for native
or physically beneficiated products manufacturing. Economies of
scale come into effect only when large amounts of materials are
processed, and thus automation requirements are imposed by the
need to handle more material than a person can reasonably lift
and carry unaided.
The Eagle report assumes that the operation of this plant will
require full time lunar base coverage. A production rate of 26
metric tons of liquid oxygen per month will require the mining of
about 2500 metric tons of feedstock assuming 10 percent ilmenite in
the feedstock material. This figure, by the way, is turning out to
be over-optimistic.
Current projects show ilmenite recovery of under 1%, thus
imposing additional beneficiation requirements to concentrate the
ore [12, 22].
The Eagle figure requires over 180 loads/month using an
8 cubic meter capacity regolith hauler. Along with the system
monitoring, response to alarms and plant problems and maintenance,
operations will require 4 full time IVA crew working in shifts.
During some short term plant problem situations, more lunar base
personnel may be required to provide a 2-man EVA team to resolve the
problem while the normal plant operator monitors the situation and
assists via lunar base teleoperation.
During the day, sunlight can be used indirectly as a source of
photovoltaic electricity. If nuclear power is a viable alternative,
reliance on solar power can be minimized. Recent studies [12]
suggest that sunlight cannot be used directly as a heat source by
the use of sun-tracking mirrors, due to problems of mirror and
window contamination.
Specific tasks that the LLOX production facility will perform are
the following:
(1) Refine/Preprocess Ore (Crush/Screen)
(2) Process Ore
(3) Liquify & Store Oxygen
(4) Remove Tailings
(5) Perform Fault Detection & Prediction
(6) Maintain/Repair/Replace Parts
What follows is a brief task description discussion on each one of these tasks.

2.1 Crush and Screen Ore

Crush and Screen Ore:
This is a purely mechanical process so automation should be the
primary approach.
Crushing is technically a size modification preconditioning, and
is closely related to grinding, which accomplishes a further
reduction. Both involve higher pressures than unaided people can
exert, and involve mechanical stresses which present a degree of
hazard to humans, so automation is clearly required.
Screening, or sieving, is a size control/separation
preconditioning process, and involves material flow and vibration
which are best isolated from human beings by some degree of
automation.
"Lunar soils or rocks can be mined as sources of ilmenite for
producing oxygen. However, seperable crystals of loose ilmenite
in lunar soils are rare (less than 2%) and small (less than 200 micrometers);
most ilmenite in the regolith is locked together with silicate
minerals as rock fragments. If fragmentation of rocks is
attempted to win appreciable amounts of ilmenite (roughly 10% or more),
selective collection of high-Ti basalt fragments larger than 1 cm
may be advantageous over extensive processing of fine lunar soil.
Many alternative schemes for fragmenting rocks on the Moon have
been proposed; one process which was tested early in the Apollo
program successfully disaggregated lunar and terrestrial basalts
by passive exposure to low-pressure alkali (K) vapor. This
process is worthy of reinvestigation" [22].

2.2 Process Ore

Process Ore: This is a primarily chemical and electrochemical
process so automation should be the primary approach.
Processing may involve physical or chemical beneficiation (see
Appendix E) with pressures, temperatures, corrosives, and
poisonous reagents which represent a hazard to humans.
Hazardous voltages and currents may be involved in three classes
of electrochemical approaches being considered for lunar
processing:
1. Direct electrolysis of lunar soil or beneficiated fractions.
2. Electrolysis of lunar soil fractions dissolved in fused salt
(fluoride, chloride, or carbonate) solvents.
3. Electrolysis of sodium hydroxide (or chloride) followed by
indirect reduction of aluminum, silicon, and other desired
constituents as in a proposed flow sheet.
Technical problems associated with these methods, and the
automation issues raised, include:
1. Direct electrolysis: (a) solving anode corrosion problems, and
possibly requiring robots to remove and install heavy electrodes
from the process plant; (b) operating with higher viscosity melts
and successfully recovering oxygen, but higher viscosity
materials run greater risks of pipe and orifice blockage which
may need to be cleared by robotic or teleoperated means; (c)
developing secondary refining methods to separate constituents
from alloys obtained, but this will introduce a greater variety
of tasks, leading to either an increased requirement for the
generality and flexibility of automation, or a greater number of
specialized automated processes and devices.
2. Electrolysis of lunar soil fractions dissolved in fused salt
solvents: (a) purification and recycling fused salt solvents,
which introduces new processing tasks for automation, and higher
overall risk; (b) avoiding carbon formation in reduction of
carbonate melts, or else automating the tricky and tedious job of
scraping carbon from containers, electrodes, and other surfaces;
(c) development of bipolar cells (if needed); (d) attrition of
reagents, which means a risk of contamination of human or
telerobotic devices by escaping chemicals; (e) developing
secondary refining methods for alloys, for which see 1(e) above.
3. Electrolysis of sodium hydroxide or chloride: sodium hydroxide
is a powerful alkali, itself hazardous to humans; (a)
effectiveness of proposed drying cycle for modified Castner cells
used in the recovery of sodium in various recycle loops; but
metallic sodium is considered hazardous for humans, due to fire
and explosive risk in the presence of oxygen or water; (b)
indirect recovery of oxygen with chlorine formed if Downs cell
sodium route is chosen; chlorine is corrosive and poisonous to
both humans and metallic robots.
Electrodialysis is a useful technique in various stages of
aqueous processing of lunar materials. Extension to nonaqueous
solvents would require additional research and development money
which might better be spent on automation and robotics,
especially as these some of these options involve high
temperatures and/or hazardous chemicals.

2.3 Liquify & Store Oxygen

Liquify & Store Oxygen: This is a purely mechanical process
so automation should be the primary approach.
Liquid oxygen is a cryogenic material, whose degree of coldness
is a hazard to humans, thereby necessitating some degree of
automation. In addition, there is a fire and explosion risk,
threatening to both humans and automated systems.
"Oxygen liquefaction is a key processing step of proposed lunar
oxygen production plants.... An aspect of most all chemical
processes is the removal of waste heat. Terrestrial chemical
processing plants typically rely on the convection of air. The
complexity of this task is greatly increased on the lunar surface
due to the lack of an atmosphere and fluids. Heat rejection will
be achieved by transferring the process heat to a cooling fluid
which in turn flows through a heat rejection device.
[Alternatives include] conduction to the lunar regolith and
radiation into deep space Ò [31, 32].

2.4 Remove Tailings

Remove Tailings: In most cases, the level of automation for
this process should be the same as that required to haul the ore
to the pre-processor. However, some of the processes produce
molten byproducts, whose removal would require other systems,
presumably at the same level of automation.

2.5 Perform Fault Detection & Prediction

Perform Fault Detection & Prediction: This process should be
automated as a caution and warning system from the outset.
This process will be among the most straightforward to enhance
with more autonomous capabilities.

2.6 Maintain/Repair/Replace Parts

Maintain/Repair/Replace Parts: This can be among the most
dangerous yet most delicate operations. Human participation
will be required to a large degree for the foreseeable future.
However, the dangerousrepair jobs would best be done telerobotically.
Ultimately, a supervised approach would be desirable. But as this requires
the development of sophisticated sensor, motor, and
software capabilities, this task will be slower to mature than the above.

2.7 Ballistic Transport

There is an alternative for ore transport which limits the
requirements for a regolith hauler. This is the concept of
ballistic transport [11].
Due to the lack of a lunar atmosphere and low lunar gravity, it
is possible that material can be thrown long distances to a small
central collection point. Transport over tens of kilometers
seems reasonable. The throwing process is more energy intensive
than hauling, ecept for very deep pit mines, but would be quick,
very flexible, and minimize the need for rolling stock (i.e.
regolith haulers).
Because of the velocity of thrown material, there is a degree of
hazard for people to manually operate such a system.
Teleoperation appears to be an unneccessary use of human
operator time. This is a likely candidate for supervised robotic
operations. The process would go on for days at a time with no
human intervention. A human supervisor would occassionally
monitor velocity dispersion, throw trajectory, angle of repose of
the pile where material accumulates, and similar parameters.
People should not be too near the reception point while material
is being thrown there.

Process Comparison:
- Most processes have not been studied in depth.
- Alternative processes to ilmenite reduction and magma
electrolysis must be studied.
- Studies must consider development costs, total facility capital
costs and operating costs.
- Initial lift weights must be considered.
- Hardware complexity must be considered.
- Studies must consider Earth-resupply.

3.2 Power-Up

Power-Up:
- The safety issues of high temperature (1350 deg. C), high
amperage (420,000 amps), and seal integrity for
dangerous material containment favor the use of remote power-up.
Automatic and remote control
power-up capability should be built into the equipment
to minimize the danger to teleoperated devices.

3.3 Power Requirements/Operation Duty Cycle

Power Requirements/Operation Duty Cycle:
- Nighttime power requirements vs. power-down/power-up shock and
production efficiency must be addressed. Duty cycles as low as
45% will be imposed if sole reliance on solar power is enforced. If
the processing plant is powered down at night and powered up at
dawn, the plant and the control regime must be designed to
accomodate the mechanical shock which could otherwise
severely stress components of the plant.
Strict control of plant conditions, process
evolution, and fault detection and continuous system health monitoring
will be necessary to protect against these thermal shock
effects. The plant can be made to run continuously (as high as
95% duty cycle) if a nuclear power plant with sufficient power
to run the facility is emplaced. However, this raises political
and environmental issues which may preclude this approach,
and promote alternatives such as hybrid systems with photovoltaic
with regenerative fuel cells, or photovoltaic with thermal
storage.
Alternate methods of storing energy for nighttime use such as
gravity mills (in which dust and rocks are dropped into a rille
onto a paddle wheel type turbine) may offer a reasonable
compromise. Processes which produce molten magma can store
a portion of the output to provide thermoelectric power to
maintain hot standby conditions, thereby precluding a range of
problems.
- Power allocation will be a dynamic activity involving planning
and resource management. Automation of this activity would free
humans for more interesting tasks. This is especially true at
night when solar power is unavailable and processes are
competing for scarce energy resources thus imposing stringent
constraints on task scheduling.

3.4 Safety Issues

Safety Issues:
- Due to the high temperatures and volume of the material being
processed, the LLOX plant will be placed sufficiently far from
the hab module to minimize personnel danger
in the event of a major process upset.
To minimize the probability of a catastrophic
failure, automatic shutdown capability must be built into the
plant. These safety features may be effected by a
combination of smart (active) and dumb (passive)
mechanisms.

3.5 Configuration Issues

Configuration Issues:
- Both the magma electrolysis and the ilmenite reduction process
will require real-time modification of operational parameters
such as electrode position, current and voltage levels, etc. to
maximize the efficiency of the processing plant. This can be
accomplished with currently available process control
strategies.

4.0 Conclusions

The efficient generation of lunar oxygen is critical to the long
term goals of the human space exploration initiative. To assure the
success of this project, the most economically efficient method of oxygen
extraction must be exploited. Also, an efficient automated process
must be established from the acquisition of raw material to the
disposal of the tailings and the storing of liquified oxygen.
Monitoring the process of extracting oxygen from lunar regolith is
very tedious. Ancillary activities such as maintenance and repair
can be dangerous. The use of between four and six personnel for
tasks of this nature is a waste of human resources and indicates the
processes to be a prime candidates for automation.
The full scale production plant will not be emplaced until flight 23
[1]. By this time, considerable equipment will already be at the
lunar site. The regolith haulers will initially be operated
telerobotically. However, they too should be designed with upgrade
in mind.
Since many of the operations of LLOX production are dangerous,
automation is essential from the outset. Neither of the two oxygen
extraction processes being considered rely on sophisticated sensor
or actuator capabilities. Due to the repetitive nature and well
defined domain of this task, the LLOX production operation offers
perhaps the best platform for the initial implementation of
autonomous systems.